This invention relates to offshore well completions and, more particularly, to the securement of pipelines to subsea wellheads.
In the construction of offshore wells, such as for the recovery of petroleum or natural gas, a well is drilled and pipelines are connected to the wellhead for conducting petroleum or natural gas to a collecting station. The actual hook-up of the pipelines must be made on the seabed. Considerable effort and difficulty is involved in accurately positioning the pipelines relative to the wellhead and performing the necessary connection activities. Proposals have been made for facilitating such operations, as exemplified in Otteman et al. U.S. Pat. Nos. 3,378,066 issued Apr. 16, 1968, Peterson 3,604,731 issued Sept. 14, 1971, Nolan 3,701,261 issued Oct. 13, 1972, Daughtry 3,775,986 issued Dec. 4, 1973, and Liautand 3,846,992 issued Nov. 12, 1974.
Some prior systems utilize a pipeline anchor which is attached directly to the wellhead or the wellhead base, and which receives and secures the pipelines for subsequent connection to the wellhead. One problem associated with such an arrangement is that undue stress may be imposed on the wellhead during subsequent pipeline hook-ups or pipe laying operations due to the anchoring of the anchor by means of the wellhead. Moreover, many anchors of this type cannot be easily repositioned to coincide with the pipeline orientation. Such systems are also vulnerable to stresses imposed by thermally induced changes in pipeline length.
In cases where pipelines are laid away from the wellhead, anchors have been proposed whereby the pipeline can be pulled by cable to the anchor for proper alignment and securement. However, such anchors are of no utility in cases where pipeline means are laid toward (rather than away from) the wellhead.
While many pipeline-to-anchor hook-ups are intended to be conducted by remote control from a surface vessel, these procedures are expensive and complex and are not needed at shallower depths which are accessible to divers. At shallower depths, then, it would be desirable to simplify diver efforts in pipeline-to-wellhead hook-up.
It is, therefore, an object of the present invention to minimize or obviate problems of the type discussed above.
It is another object of the invention to provide novel methods and apparatus for securing offshore pipeline to subsea installations.
It is a further object of the invention to simplify diver efforts during the hook-up of pipelines to subsea wellheads.
It is an additional object of the invention to enable subsea pipeline hook-ups to be made without imposing loads that cause undue stress on a wellhead and in such a manner as to tend to isolate thermally induced pipeline stress from a wellhead.
It is yet another object of the present invention to provide a novel subsea flowline anchor which can be reoriented subsequent to being positioned on the seabed, and/or prior thereto.
It is a further object of the invention to provide a novel subsea flowline anchor which selectively facilitates the hook-up of pipelines laid either toward or away from the wellhead.
It is one additional object of the present invention to provide a flowline anchor which is secured to the seabed for positioning relative to the wellhead by means of a pin pile which isolates the wellhead from forces generated in anchoring flowlines to the anchor and from thermally induced pipeline stress.
It is yet another object of the present invention to provide a selectively positionable subsea flowline anchor which includes an inclined ramp for receiving pipeline means laid toward a wellhead, and a pivoted socket for receiving pipeline laid away from the wellhead.